Several common immunoassay techniques utilize solid support-antibody complexes to accomplish the detection of specific antigens or antibodies in the sample serum. See, e.g., the immunoassay methods described in U.S. Pat. No. 4,376,110, the relevant portions of which are hereby incorporated by reference into the present application. Typically, the solid support is a plastic bead. After the sample serum and antibody-solid support complex have been incubated for a period of time in the presence of a conjugate, a wash step is required to remove unbound chemical species from the solid support prior to the introduction of reagents; which are used in subsequent reactions which reactions result in the formation of a measurable characteristic, e.g., fluorescence. Immunoassay techniques, however, are extremely sensitive. The presence of trace amounts of unbound components can dramatically affect the subsequent reactions and thereby alter the assay results. When the immunoassay technique is performed manually, the bead can be soaked for a period of time to remove all traces of unreacted materials. The washing step can also be repeated several times to accomplish the desired result. A more completed description of the requirements and suggested techniques for this wash step can be found in the product literature which accompanies Tandem-E Immunoassay Kits marketed by Hybritech, Inc., San Diego, Ca. The relevant portions of that product literature are hereby incorporated by reference into this application.
In the automation of immunoassay techniques, an extended soaking period is not possible if the instrument is to be capable of completing one rack of reaction tubes before the end of an incubation period for a second rack of tubes. Without soaking, however, the twenty-five parts per million specification of the assay protocol is difficult to meet.
The instant invention makes possible the automation of the wash step providing methods and apparatus which are capable of removing unbound components and serum from reaction tubes in a suitably short period of time while simultaneously accomplishing the twenty-five parts per million specification.
It is therefore an object of this invention to provide apparatus and methods which make possible the automation of the routine operation of removing unreacted components from the solid support and reaction tube used in immunoassay techniques.
It is a further object of this invention to provide a simple system for performing the wash step on a rack of reaction tubes in a short cycle time, thereby enabling sufficient through-put to meet the demands of clinical use.
It is another object of this invention to remove unreacted components from the solid support and tubes with detergent solutions without having to remove the rack of tubes from the instrument to soak.
These, and other objects of this invention, shall become apparent to those skilled in the art with reference to this specification and the accompanying figures to which it refers.